Wristwatch restoration, servicing and repair

Posts Tagged ‘Seiko Bell-Matic’

Seiko 4006-7020 (27J Bell-Matic)…

Another 27J Bell-Matic, like the last one, a -7020 model but this time with it’s original bracelet. The watch had been ‘resting’ in a drawer for years but despite being a little untidy on the outside, the movement was in great shape with just a little wear on the edge of the train bridge caused by worn rotor bearings.

(Click pictures to enlarge)

The second hand had been replaced with one that was too long, but apart from that there was little sign that the watch had ever been opened. However, when I removed the calendar plate… Huh? A jewel for the lower mainspring barrel arbor?

As this was one of the earlier Bell-Matics (Nov. 1967) I wondered whether this was a different jewel layout, but as none of the other jewels were missing this had to be an extra. Under 10x magnification I could see that the inside of the hole was not plated, so the jewel setting must have been reamed and pressed in at a later date by a very diligent watchmaker, making this a very rare 28 jewel Bell-Matic, great! (Inset is the opposite side of the jewel with the mainspring barrel removed).

This extra jewel means that every pivot in the timekeeping side of the movement now has a jewel which reduces friction and wear, increasing accuracy. For comparison, here’s a shot of a regular main plate in which the lower mainspring arbor has worn through the plating after many years of use.

Eventually, this wear will result in too much endshake for the barrel. Under the tension of the mainspring, the barrel will then be pulled out of alignment and will not mesh smoothly with the centre wheel, affecting the timekeeping or stopping the watch.

No more surprises… so after a good cleaning, I replaced the worn winding rotor bearings, found a replacement second hand and gave the case and bracelet a light polish. I even managed to clean up the original crystal.

Here’s the result… my 28 jewel Bell-Matic.


Omega Seamaster Memomatic…

I’m sure it’s obvious to regular visitors that I’ve got a keen interest in Seiko’s Bell-Matic watches. I’m looking to broaden my knowledge of vintage alarm watches and read about Omega’s Seamaster Memomatic model from the early 70’s, which shares a lot of similarities with Seiko’s Bell-Matic, so I thought I’d compare the two.

Here’s the Memomatic, it’s a great looking watch…

(Click to enlarge – pictures by a.r.a. gallery)

The first thing to point out is that rather than having a separate bezel for setting the alarm, the Memomatic has two discs in the centre of the dial which are rotated via the crown. This allows the wearer to set the alarm to the exact minute, rather than the ‘near enough’ approach used by the Bell-Matic and most other vintage alarm mechanisms.

The adverts from the time show that this was a major selling point for Omega, but looking closely at the service manual, a tolerance of +/-4 minutes is deemed acceptable when testing the alarm triggering mechanism, which makes it no more accurate than the Bell-Matic. Doesn’t this actually defeat the whole purpose of setting the alarm to the minute? Strange!

It has a very similar crown layout and operation to the Bell-Matic except that the alarm time can be set both clockwise and anticlockwise via the winding crown and date quickset is performed by pressing the recessed button between the crowns. The Memomatic mainspring can also be hand wound, the Bell-Matic cannot. (A scan of the full Memomatic user manual can be found here).

The engine in the Memomatic is Omega’s 980 calibre, which has 19 jewels and is slightly smaller in diameter than the Seiko at 30.8mm, (Seiko’s 4006A is 31.2mm) but slightly thicker at 7.8mm (the Seiko is 7.15mm).

It runs at 21,600bph (6 beats/sec) which is slightly faster than the Seiko which runs at 19,800bph (5.5beats/sec). Notice too that, like the Bell-Matic, the 980 has an independent sounding spring around the edge of the calibre rather than the hammer impacting part of the watch case as is common in other alarm mechanisms.

The biggest advantage that the Memomatic has over the Bell-Matic is that it has only one mainspring which powers both the going train and the alarm. As this is an automatic winding calibre, this also means that the alarm never has to be wound independently. If the watch is running, the alarm should be ready to go.

Reading the technical literature on the calibre, when triggered, the mainspring barrel completes one complete revolution which sounds the alarm for 8-10 seconds (about the same length of time as the Bell-Matic). How it manages to do this while still supplying power to the going train is very intriguing to me. Even looking at the exploded diagrams in the service manual it’s hard to work out how it does this.

I’d like to get hold of one and study it in depth but that could be tricky as only 35,000 examples were made and they now change hands for around the US$800 mark. Even when available on the high street, this technology still commanded a hefty price, the Memomatic originaly retailing at a higher price than Omega’s popular Seamaster Chronograph.

I’d better start saving up….


Seiko 4006-7020 (27J Bell-Matic)…

This 27 Jewel Bell-Matic is one of the early models from 1968. From a cosmetic point of view, this one arrived in quite poor shape.

(Click pictures to enlarge)

The lume on the hands and alarm pointer in particular needed some attention but luckily, the dial was still in good shape under the scratched up crystal.

The seller said that the watch had a damaged escapement so I was prepared for a mangled hairspring, but this wasn’t the case, the balance assembly was fine. However, when the watch was shaken it ran down instantly indicating a problem with the escapement somewhere. Peering into the movement quickly revealed the problem… no escape wheel, a much easier fix than battling with a damaged hairspring! Thankfully, no other parts were missing so after a thorough cleaning and an escape wheel from the parts box, the movement started right up.

I also found that the hands had been installed without the proper tools at some stage and were bent in all directions. It took quite some effort to straighten them out. Bent hands are always a problem but especially so with Bell-Matics. When the alarm triggers, the hour wheel rises, reducing the clearance between the hour and minute hands. If the hands are in poor condition (or have not been set correctly) they will touch when they pass, either stopping the watch or worse, scratching the hour hand on the underside of the minute hand.

After sorting out all the cosmetic issues, I gave the case a light polish to get rid of any surface scratches and installed a new crystal. Quite a bit of work required this time to make this one right, but a nice end result.


The Seiko Calibre 4006…

Another comparison post, this time the 17 and 27 jewel versions of the 4006A calibre found in most of Seiko’s Bell-Matic watches. While the majority of this information can be found by digging in the archives of various forums, I thought I’d highlight the differences here with a few pictures.

The production run for the 4006A calibre is thought to have been between 1967 and 1977 and it was manufactured with three different jewel counts, 17, 21 and 27 jewels. When the watches were assembled, the calibre inside was clearly marked on the watch dial…

(Click pictures to enlarge)

Opening the caseback reveals the first difference between the calibres, the winding rotor is marked with the jewel count, which should match the dial markings if everything is in order.

Removing the rotor and winding bridge reveals the first technical difference, additional jewels for the third and fourth wheel pivots on the 27 jewel model.

(Click picture to enlarge)

Also notice that this particular 27 jewel movement has an extra long sounding spring. The longer spring isn’t fitted to all 27 jewel movements, I’ve only seen it on the really early models. (It doesn’t seem to make the alarm any louder).

Removing the ratchet wheels for both the mainspring and the alarm spring barrels reveals two more of the additional jewels, for the barrel arbors. This side by side comparison of the barrel and wheel train bridges clearly shows all four extra jewels.

The rest of the jewels can be found on the other side of the calibre under the dial and calendar mechanism. The remaining six jewels are all underneath the date ring, embedded into the calendar plate…

While these jewels do reduce friction for the date ring, six jewels for this task is overkill, which makes me think that Seiko may have been planning additional upgrades for this calibre. Here’s a side by side shot of the calendar plates showing the extra jewels.

(Click picture to enlarge)

When I compared the 6106 calibres in a previous post, I found similar jewels under the date ring on the earliest version, the 6106A. These jewels were then used in revisions B & C of the calibre, adding Diafix caps for the third and escape wheel pivots. As the 6106A and 4006A calibres were both introduced in 1967, I wonder if Seiko had similar plans for the 4006A…. a 4006B perhaps?

If a 4006B was planned, it never made it into production, Seiko opting instead to discontinue the 27 jewel version of the calibre in 1974 and finish the production run with just the 17 jewel version.

So, is it worth paying a premium for a 27 jewel Bell-Matic? I think it is. Though technically ‘functioning jewels’, the six jewels under the date ring don’t bring much to the party, but the additional jewels for the mainspring barrel arbor and the third and fourth wheel pivots means that the majority of the going train is now jewelled. This will reduce wear, increasing the accuracy and longevity of the movement. The 27 jewel models were made earlier in the production run, and there are fewer of them, which also increases their appeal and collectability.

I was hoping to include a 21 Jewel movement in this comparison but as they only had a production run of a year or so (1967-68), they are rarely seen. I’ve read that the 21 jewel model has a mixture of the upgrades here, with two extra jewels each for the calendar plate and the barrel and wheel train bridge. I’ll post again when (if?) I get hold of one.

** I’ve since acquired a 21 jewel model, read the post here **


Seiko 4006-6010 (17J Bell-Matic)…

My Bell-Matic collection is steadily growing and here’s another one that I’ve been looking out for, this great blue dialled model from 1970.

This one was running when it arrived, but was quite erratic on the timer, which gave me a good excuse to overhaul it (not that I need much of an excuse!) The second hand had been painted red at some time in its life, so I replaced it with an unpainted one to return it to its original condition.

Very little else was needed this time, the case was still in great shape, with most of the factory brushed finish still intact. So just a light crystal polish, a new strap, and it was ready to wear.


Seiko 4006-6021 (17J Bell-Matic)…

Another 17J Bell-Matic, this time from 1975. As this watch had been sitting in a drawer for the last 18 years it was no surprise that it needed a good cleaning both inside and out.

(Click pictures to enlarge)

Hiding under that scuffed up crystal was a perfect dial and alarm ring. The hands were also in great shape with near perfect paint and clean original lume which is always nice to see.

No problems mechanically on this one but I did have my first problem with aftermarket crystals. I’ve been using crystals from a German company (Sternkreuz) and although the profile is slightly different to genuine Seiko crystals, it hasn’t really been a problem up until now.

With this particular cushion shaped case, the crystal seemed to sit lower than other case styles and the different side profile trapped the alarm bezel when the case back was tightened, which stopped it from rotating. Though badly scratched, the original crystal was not cracked, so I decided to try polishing it. I couldn’t get rid of every blemish without making the crystal too thin, but it cleaned up quite nicely… as did the rest of the watch.


Seiko 4006-6070 (17J Bell-Matic)…

I picked up this box of Bell-Matic spares on eBay with the intention of adding them to my parts stock.

(Click pictures to enlarge)

But when they arrived, the movement was 75% complete and the dial and alarm ring were in near perfect condition so I decided to resurrect the watch rather than breaking it up.

I disassembled and cleaned the partial movement to make sure everything was ok and I found it to be in very good shape overall, plus I had all the missing parts needed to get it up and running again, which was a bonus. There was no case included with the parts, so the watch has a temporary home in this cushion shaped case until I can find the correct case for it.

This picture shows how the watch would originally have looked.

I’m sure one will turn up eventually, but even in the wrong case, it’s still a nice looking watch and certainly deserves better than a close shave with the parts bin!


Seiko 4006-6031 (17J Bell-Matic)…

I’ve really taken a shine to Seiko’s Bell-Matics and though I’d done my homework, I still took a bit of a risk winning an eBay auction with this blurry picture…

(Click pictures to enlarge)

… but the risk paid off this time as the watch was all original, the hands, dial and alarm ring looked in excellent condition beneath the damaged crystal.

The watch didn’t run, and though the alarm did ring, it triggered as soon as the alarm button was pulled out. I put this down to a lubrication problem as the rest of the movement was pretty dry, but even when cleaned and oiled it had the same problem. After taking the alarm mechanism apart several times thinking it must be an adjustment issue, I finally tracked down the problem to a worn alarm disconnecting lever.

This lever is pressed down by the hour wheel arresting the alarm hammer until the chosen alarm time comes around. The disconnecting lever then rises, freeing the alarm hammer which moves back and forth beneath it, striking the sounding spring.

In this case, the wear on the disconnecting lever meant that it could not be depressed far enough to stop the alarm hammer, so the alarm would ring immediately when set. I’m steadily accumulating a few spare parts for this calibre so I swapped out the worn lever for one in better condition which solved the problem.

Here’s the results of a service, a new crystal and some refinishing work on the case.

This is a very popular model and has been on my Bell-Matic ‘most wanted list’ for a while now. Looking at that rich blue dial, it’s not hard to see why!